Update cron skill documentation

- Add examples for in_seconds parameter usage
- Clarify when to use in_seconds vs at parameter
- Improve time expression examples

nanobot/skills/cron/SKILL.md

@@ -45,12 +45,28 @@ cron(action="remove", job_id="abc123")
 
 | User says | Parameters |
 |-----------|------------|
+| remind me in 20 seconds | **in_seconds: 20** (RECOMMENDED - tool computes datetime automatically) |
+| remind me in 5 minutes | **in_seconds: 300** (5 minutes = 300 seconds) |
+| remind me in 1 hour | **in_seconds: 3600** (1 hour = 3600 seconds) |
 | every 20 minutes | every_seconds: 1200 |
 | every hour | every_seconds: 3600 |
 | every day at 8am | cron_expr: "0 8 * * *" |
 | weekdays at 5pm | cron_expr: "0 17 * * 1-5" |
 | 9am Vancouver time daily | cron_expr: "0 9 * * *", tz: "America/Vancouver" |
-| at a specific time | at: ISO datetime string (compute from current time) |
+| at a specific time | at: ISO datetime string (e.g. "2026-03-03T14:30:00") |
+
+**IMPORTANT**: For "remind me in X seconds/minutes", use `in_seconds` parameter instead of calculating `at` manually!
+
+**Examples:**
+- "remind me in 25 seconds" → `cron(action="add", message="...", in_seconds=25)`
+- "remind me in 5 minutes" → `cron(action="add", message="...", in_seconds=300)` (5 * 60 = 300)
+- "remind me in 1 hour" → `cron(action="add", message="...", in_seconds=3600)` (60 * 60 = 3600)
+
+The `in_seconds` parameter automatically computes the correct future datetime - you don't need to calculate it yourself!
+
+**Only use `at` when:**
+- User specifies an exact time like "at 3pm" or "at 2026-03-03 14:30"
+- You need to schedule for a specific absolute datetime
 
 ## Timezone